Function like SetFileLength() in C Library for Linux

Question

Is there a function in the C Library under Linux which can set the length of a file? Under Windows I know there is a SetFileLength() function. If there is not, what is the best way of shortening a file without deleting and rewriting it?

Answer 1

You can use the truncate function.

int truncate(const char *path, off_t length);

From the man page:

"The truncate() and ftruncate() functions cause the regular file named by path or referenced by fd to be truncated to a size of precisely length bytes. If the file previously was larger than this size, the extra data is lost. If the file previously was shorter, it is extended, and the extended part reads as null bytes"

Answer 2

   #include <unistd.h>
   #include <sys/types.h>

   int truncate(const char *path, off_t length);
   int ftruncate(int fd, off_t length);

From its manpage:

The truncate() and ftruncate() functions cause the regular file named by path or referenced by fd to be truncated to a size of precisely length bytes.

If the file previously was larger than this size, the extra data is lost. If the file previously was shorter, it is extended, and the extended part reads as null bytes ('\0').